With the application of sensor networks in industrial, commercial, and medical areas, sensor operating system should be revisited to handle dependability problem. In this paper, we present a novel component-based sensor operating system, MTOS (Micro-Transformers Operating System), which supports adaptive dynamic reconfiguration for resource-constrained sensor nodes to achieve dependability. Through error-driven reconfiguration and change-driven reconfiguration, MTOS can push a system into a stable state in which errors can be recovered with minimized side effects and changes can be safely made without interruption of normal services. The experimental results show that our approach can improve the dependability efficiently.